w1: new w1_ds2406 driver

Some preliminary work at making use of this driver led me to implement
CRC-16 checks on read and write to deal with the occasional glitchiness of
the 1-Wire bus.  The revised driver (attached) returns an I/O error if the
CRC check fails.  When reading the chip's state, either you get a valid
indication or you get an I/O error.  When changing its state, either the
change is successful or an I/O error is returned.

Signed-off-by: Scott Alfter <scott@alfter.us>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 168 insertions, 0 deletions

diff --git a/drivers/w1/slaves/w1_ds2406.c b/drivers/w1/slaves/w1_ds2406.c
new file mode 100644
index 000000000000..d488961a8c90
--- /dev/null
+++ b/drivers/w1/slaves/w1_ds2406.c
@@ -0,0 +1,168 @@
+/*
+ * w1_ds2406.c - w1 family 12 (DS2406) driver
+ * based on w1_ds2413.c by Mariusz Bialonczyk <manio@skyboo.net>
+ *
+ * Copyright (c) 2014 Scott Alfter <scott@alfter.us>
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2. See the file COPYING for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/device.h>
+#include <linux/types.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/crc16.h>
+
+#include "../w1.h"
+#include "../w1_int.h"
+#include "../w1_family.h"
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Scott Alfter <scott@alfter.us>");
+MODULE_DESCRIPTION("w1 family 12 driver for DS2406 2 Pin IO");
+
+#define W1_F12_FUNC_READ_STATUS		   0xAA
+#define W1_F12_FUNC_WRITE_STATUS	   0x55
+
+static ssize_t w1_f12_read_state(
+	struct file *filp, struct kobject *kobj,
+	struct bin_attribute *bin_attr,
+	char *buf, loff_t off, size_t count)
+{
+	u8 w1_buf[6]={W1_F12_FUNC_READ_STATUS, 7, 0, 0, 0, 0};
+	struct w1_slave *sl = kobj_to_w1_slave(kobj);
+	u16 crc=0;
+	int i;
+	ssize_t rtnval=1;
+
+	if (off != 0)
+		return 0;
+	if (!buf)
+		return -EINVAL;
+
+	mutex_lock(&sl->master->bus_mutex);
+
+	if (w1_reset_select_slave(sl)) {
+		mutex_unlock(&sl->master->bus_mutex);
+		return -EIO;
+	}
+
+	w1_write_block(sl->master, w1_buf, 3);
+	w1_read_block(sl->master, w1_buf+3, 3);
+	for (i=0; i<6; i++)
+		crc=crc16_byte(crc, w1_buf[i]);
+	if (crc==0xb001) /* good read? */
+		*buf=((w1_buf[3]>>5)&3)|0x30;
+	else
+		rtnval=-EIO;
+
+	mutex_unlock(&sl->master->bus_mutex);
+
+	return rtnval;
+}
+
+static ssize_t w1_f12_write_output(
+	struct file *filp, struct kobject *kobj,
+	struct bin_attribute *bin_attr,
+	char *buf, loff_t off, size_t count)
+{
+	struct w1_slave *sl = kobj_to_w1_slave(kobj);
+	u8 w1_buf[6]={W1_F12_FUNC_WRITE_STATUS, 7, 0, 0, 0, 0};
+	u16 crc=0;
+	int i;
+	ssize_t rtnval=1;
+
+	if (count != 1 || off != 0)
+		return -EFAULT;
+
+	mutex_lock(&sl->master->bus_mutex);
+
+	if (w1_reset_select_slave(sl)) {
+		mutex_unlock(&sl->master->bus_mutex);
+		return -EIO;
+	}
+
+	w1_buf[3] = (((*buf)&3)<<5)|0x1F;
+	w1_write_block(sl->master, w1_buf, 4);
+	w1_read_block(sl->master, w1_buf+4, 2);
+	for (i=0; i<6; i++)
+		crc=crc16_byte(crc, w1_buf[i]);
+	if (crc==0xb001) /* good read? */
+		w1_write_8(sl->master, 0xFF);
+	else
+		rtnval=-EIO;
+
+	mutex_unlock(&sl->master->bus_mutex);
+	return rtnval;
+}
+
+#define NB_SYSFS_BIN_FILES 2
+static struct bin_attribute w1_f12_sysfs_bin_files[NB_SYSFS_BIN_FILES] = {
+	{
+		.attr = {
+			.name = "state",
+			.mode = S_IRUGO,
+		},
+		.size = 1,
+		.read = w1_f12_read_state,
+	},
+	{
+		.attr = {
+			.name = "output",
+			.mode = S_IRUGO | S_IWUSR | S_IWGRP,
+		},
+		.size = 1,
+		.write = w1_f12_write_output,
+	}
+};
+
+static int w1_f12_add_slave(struct w1_slave *sl)
+{
+	int err = 0;
+	int i;
+
+	for (i = 0; i < NB_SYSFS_BIN_FILES && !err; ++i)
+		err = sysfs_create_bin_file(
+			&sl->dev.kobj,
+			&(w1_f12_sysfs_bin_files[i]));
+	if (err)
+		while (--i >= 0)
+			sysfs_remove_bin_file(&sl->dev.kobj,
+				&(w1_f12_sysfs_bin_files[i]));
+	return err;
+}
+
+static void w1_f12_remove_slave(struct w1_slave *sl)
+{
+	int i;
+	for (i = NB_SYSFS_BIN_FILES - 1; i >= 0; --i)
+		sysfs_remove_bin_file(&sl->dev.kobj,
+			&(w1_f12_sysfs_bin_files[i]));
+}
+
+static struct w1_family_ops w1_f12_fops = {
+	.add_slave      = w1_f12_add_slave,
+	.remove_slave   = w1_f12_remove_slave,
+};
+
+static struct w1_family w1_family_12 = {
+	.fid = W1_FAMILY_DS2406,
+	.fops = &w1_f12_fops,
+};
+
+static int __init w1_f12_init(void)
+{
+	return w1_register_family(&w1_family_12);
+}
+
+static void __exit w1_f12_exit(void)
+{
+	w1_unregister_family(&w1_family_12);
+}
+
+module_init(w1_f12_init);
+module_exit(w1_f12_exit);